1. Field of the Invention
The present invention relates generally to non-aerosol fluid dispensers, such as trigger sprayers. More particularly, the invention concerns a highly efficient pump for such dispensers, wherein the pump provides consistent discharge amounts and may be formed of the same material as the other dispenser components for facilitating recycling.
2. Discussion of the Prior Art
Non-aerosol fluid dispensers (or so-called "mechanical sprayers") have numerous and various applications, such as trigger sprayers for spraying liquid cleaning solutions, perfume sprayers, lotion dispensers, etc. The rising popularity of such dispensers may be attributed to several factors. For example, environmental concerns surrounding aerosol sprayers have steered development toward mechanical sprayers that eliminate the need of aerosol or gas charged containers. Further, developments in mechanical sprayer designs have increased the discharge amount and duration and allow the operator to vary the spray pattern.
Conventional mechanical sprayers include a variety of features that have become common and well-known in the industry. For example, pressure-responsive supply and discharge valves are spaced along a fluid path extending between a container and a fluid outlet. A pump defining a collapsible fluid chamber is associated with the fluid path between the valves so that the supply valve is located between the chamber and the container, and the discharge valve is located between the chamber and outlet. Accordingly, positive pressure produced when the chamber collapses causes the supply valve to close and the discharge valve to open so that fluid is dispensed through the outlet. Conversely, negative pressure produced when the chamber expands causes the supply valve to open and the discharge valve to close so that the chamber is primed with fluid from the container. As noted above, the present invention is primarily concerned with the pump and the problems associated with the various conventional pump constructions exemplified hereinbelow.
One of the most common pumps used in mechanical sprayers comprises a piston slidably disposed within a cylindrically-shaped, hollow accumulator. The piston and accumulator cooperatively define a chamber that collapses and expands as the piston is slid back-and-forth within the accumulator. A metal spring is typically disposed within the chamber for yieldably biasing the piston away from one end of the accumulator. Accordingly, fluid is discharged when the piston is manually slid toward the one end of the accumulator, and the accumulator is primed when the piston is released so that the spring slides the piston away from the one end. The piston and accumulator sealingly engage one another to prevent leakage during operation of the dispenser. Further, the piston and accumulator are formed of dissimilar materials, such as polyethylene and polypropylene, so as to allow sealed yet slidable interengagement therebetween.
The accumulator-type pump presents several problems. For example, the accumulator, piston and spring must be separately manufactured and later assembled, thereby increasing production time and costs. Additionally, recycling of the dispenser is problematic because the accumulator, piston and spring are each formed of dissimilar materials, as indicated above.
Another type of pump for mechanical sprayers comprises a resilient, hollow bulb-shaped body defining an interior fluid chamber communicating with the fluid path. Such pumps are difficult to manufacture and are often formed of expensive rubber materials. Further, collapsing of the body is often uncontrolled and therefore may vary from one operation to another, whereby the discharge amount has a tendency to be inconsistent. That is, the body has a tendency to variously flex in random amounts and directions, when it is collapsed, such that the volumetric reduction of the interior chamber varies from one operation to another.
Bellows pumps are also often used in mechanical sprayers. Conventional bellows have taken a variety of shapes, including axially collapsible bellows, "blacksmith" bellows, etc. In any case, bellows pumps often collapse in a nonuniform manner and therefore likewise present the problem of inconsistent discharge amounts. Moreover, a conventional bellows pump is not completely purged when collapsed, and consequently, air is often trapped within the fluid chamber. Because air is naturally more compressible and expandable than the dispensed fluid, the efficiency of the pump is significantly reduced. In other words, when negative or positive pressure is created within the pump chamber, the air absorbs a significant portion of the energy such that the pressure is less productive in inducing or discharging fluid into or out of the chamber. For example, as the bellows expands, the negative pressure created within the chamber not only draws fluid from the container but also causes the trapped air to expand. Furthermore, should any of the trapped air be discharged with the fluid, the highly undesirable phenomenon known as "spitting" occurs. It will be appreciated that accumulator-type and bulb-type pumps are likewise inefficient because the fluid chamber is never completely evacuated (i.e., the spring prevents evacuation of the accumulator and the bulbous body in a bulb-type pump is not depressed in a manner to completely collapse the chamber).